No, Express Gate is completely different. UEFI directly replaces the BIOS....Express Gate does not.
The Asus Express Gate is a software application installed in the firmware of newer Asus motherboards. Express Gate acts as a mini operating system, offering the user access to mini-games, their photos, instant messenger programs, Skype, the Web, and more, within 5 seconds of powering on their PC. Express Gate loads immediately, prior to the computer entering the main operating system, be it Linux, Windows, or other.